1. Field of the Invention
The invention relates to a process for the automatic detection of defects in mechanical parts of complex geometry by inspection of a radioscopic image of the part, and is particularly applicable in the field of aeronautics to the automatic appraisal of blade castings which are inspected radioscopically.
2. Summary of the Prior Art
Non-destructive radioscopic inspection has hitherto been limited to the checking of parts having a simple geometry. For parts of this type, the radioscopic images comprise assessable zones of homogenous appearance in which the variations in the grey levels are of the low frequency type and in which possible defects are looked for after the employment of image processing operations such as morphological transformations and linear filtering.
These image processing operations are determined from standard formative elements of predetermined size and shape and assume that the assessable zones of the image are infinite wholes, all the points of the image having the same number of adjacent points (this condition is not in fact true at the limits of the assessable zones).
In the case of parts with complex geometry the radioscopic image has a texture including zones of low contrast which are bereft of useful information and which constitute non-assessable zones. These non-assessable zones are superimposed on the assessable zones of the image, and the application of conventional image processing operations gives erroneous results due to the effect of the zones which are devoid of useful data. The low contrast or saturated zones in fact represent discontinuities in the assessable zones, which can no longer be regarded as infinite wholes.
It is an object of the invention therefore to provide a process for the automatic detection of defects which can be applied to parts of complex geometry, whose radioscopic image comprises assessable zones having a gradient of grey levels and on which saturated zones which are very light or very dark and comprise no useful data are superimposed.